This invention relates to iron disulfide (FeS.sub.2) electrodes for high temperature, molten salt batteries such as lithium/alkali metal halide/iron disulfide batteries (e.g., Li/LiCl-KCl/FeS.sub.2). The overall reaction for that battery is essentially: EQU 4Li + FeS.sub.2 .revreaction. Fe + 2Li.sub.2 S
wherein the Li and the FeS.sub.2 are respectively the negative and positive electrodes which, during discharge, combine electrochemically (after a number of intermediate steps) to form iron and lithium sulfide.
The lithium in the negative electrode may be either a liquid or a solid. In the liquid state, the lithium is typically capillarily contained within the interstices of a porous wick or matrix (typically metal) such as is disclosed in Craig U.S. Pat. No. 3,560,265 (issued Feb. 2, 1971) or Bradley et al. U.S. Pat. No. 3,532,549 (issued Oct. 6, 1970). In the solid state, the lithium is typically alloyed with another material (e.g., aluminum or silicon) which raises its melting point above the cell operating temperature, but also reduces its effectiveness.
The iron disulfide in the positive electrode is a granular material and, as such, has required means for substantially immobilizing the granules while they are being integrated into the electrode during assembly. Normally binders (i.e., permanent or temporary) are used for this purpose. Temporary binders are removed, as best as possible, after the FeS.sub.2 -binder has been integrated with appropriate current collectors during assembly. Substantially complete removal of the binder from the FeS.sub.2 in the electrode has been considered essential to long-lived cells which are intolerant of impurities. In this regard, these cells are so impurity sensitive that even the construction materials are preferably purified to reduce the likelihood of cell contamination, since some contaminents accelerate corrosive attack of the cell's construction materials, while others, particularly those which form gas bubbles at cell operating temperatures, are particularly deleterious to the electrode's effectiveness.
It is an object of the present invention to prepare iron disulfide electrodes by temporarily immobilizing the FeS.sub.2 in an easily useable, readily-removable, and chemically/electrochemically compatible binder during its integration with the electrode's current collectors.